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Useful Mutants, Bred With Radiation

VIENNA — Pierre Lagoda pulled a small container from his pocket and spilled the contents onto his desk. Four tiny dice rolled to a stop.

“That’s what nature does,” Dr. Lagoda said. The random results of the dice, he explained, illustrate how spontaneous mutations create the genetic diversity that drives evolution and selective breeding.

He rolled the dice again. This time, he was mimicking what he and his colleagues have been doing quietly around the globe for more than a half-century — using radiation to scramble the genetic material in crops, a process that has produced valuable mutants like red grapefruit, disease-resistant cocoa and premium barley for Scotch whiskey.

“I’m doing the same thing,” he said, still toying with the dice. “I’m not doing anything different from what nature does. I’m not using anything that was not in the genetic material itself.”

Dr. Lagoda, the head of plant breeding and genetics at the International Atomic Energy Agency, prides himself on being a good salesman. It can be a tough act, however, given wide public fears about the dangers of radiation and the risks of genetically manipulated food. His work combines both fields but has nonetheless managed to thrive.

The process leaves no residual radiation or other obvious marks of human intervention. It simply creates offspring that exhibit new characteristics.

Though poorly known, radiation breeding has produced thousands of useful mutants and a sizable fraction of the world’s crops, Dr. Lagoda said, including varieties of rice, wheat, barley, pears, peas, cotton, peppermint, sunflowers, peanuts, grapefruit, sesame, bananas, cassava and sorghum. The mutant wheat is used for bread and pasta and the mutant barley for beer and fine whiskey.

The mutations can improve yield, quality, taste, size and resistance to disease and can help plants adapt to diverse climates and conditions.

Dr. Lagoda takes pains to distinguish the little-known radiation work from the contentious field of genetically modified crops, sometimes disparaged as “Frankenfood.” That practice can splice foreign genetic material into plants, creating exotic varieties grown widely in the United States but often feared and rejected in Europe. By contrast, radiation breeding has made few enemies.

“Spontaneous mutations are the motor of evolution,” Dr. Lagoda said. “We are mimicking nature in this. We’re concentrating time and space for the breeder so he can do the job in his lifetime. We concentrate how often mutants appear — going through 10,000 to one million — to select just the right one.”

Politically, the method is one of many quid pro quos the agency, an arm of the United Nations in Vienna, offers client states. Its own agenda is to inspect ostensibly peaceful atomic installations in an effort to find and deter secret work on nuclear weapons.

Plant scientists say radiation breeding could play an important role in the future. By promoting crop flexibility, it could help feed billions of added mouths despite shrinking land and water, rising oil and fertilizer costs, increasing soil exhaustion, growing resistance of insects to pesticides and looming climate change. Globally, food prices are already rising fast.

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Photo illustration by Tony Cenicola/The New York Times

“It’s not going to solve the world food crisis,” said J. Neil Rutger, former director of the Dale Bumpers National Rice Research Center in Stuttgart, Ark. “But it will help. Modern plant breeders are using every tool they can get.”

The method was discovered some 80 years ago when Lewis J. Stadler of the University of Missouri used X-rays to zap barley seeds. The resulting plants were white, yellow, pale yellow and some had white stripes — nothing of any practical value.

But the potential was clear. Soon, by exposing large numbers of seeds and young plants, scientists produced many more mutations and found a few hidden beneficial ones. Peanuts got tougher hulls. Barley, oats and wheat got better yields. Black currants grew.

The process worked because the radiation had randomly mixed up the genetic material of the plants. The scientists could control the intensity of the radiation and thus the extent of the disturbance, but not the outcome. To know the repercussions, they had to plant the radiated material, let it grow and examine the results. Often, the gene scrambling killed the seeds and plants, or left them with odd mutations. But in a few instances, the process made beneficial traits.

In the 1950s and 1960s, the United States government promoted the method as part of its “atoms for peace” program and had notable successes. In 1960, disease heavily damaged the bean crop in Michigan — except for a promising new variety that had been made by radiation breeding. It and its offspring quickly replaced the old bean.

In the early 1970s, Dr. Rutger, then in Davis, Calif., fired gamma rays at rice. He and his colleagues found a semi-dwarf mutant that gave much higher yields, partly because it produced more grain. Its short size also meant it fell over less often, reducing spoilage. Known as Calrose 76, it was released publicly in 1976.

Today, Dr. Rutger said, about half the rice grown in California derives from this dwarf. Now retired in Woodland, Calif., he lives just a few miles from where the descendants grow, he said.

A similar story unfolded in Texas. In 1929, farmers stumbled on the Ruby Red grapefruit, a natural mutant. Its flesh eventually faded to pink, however, and scientists fired radiation to produce mutants of deeper color — Star Ruby, released in 1971, and Rio Red, released in 1985. The mutant offspring now account for about 75 percent of all grapefruit grown in Texas.

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Though the innovations began in the United States, the method is now used mostly overseas, with Asia and Europe the leading regions. Experts cited two main reasons: domestic plant researchers over the decades have already made many, perhaps most of the easiest improvements that can be achieved with radiation, and they now focus on highly popular fields like gene splicing.

“Most scientists here would say it’s pretty primitive,” Norman T. Uphoff, a professor of government and international agriculture at Cornell University, said of the method. “It’s like being in a huge room with a flashlight.”

But the flashlight is cheap, which has aided its international spread.

Today, the process usually begins with cobalt-60, a highly radioactive material used in industrial radiography and medical radiotherapy. Its gamma rays, more energetic than X-rays, can travel many yards through the air and penetrate lead.

Understandably, the exposure facilities for radiation breeding have layers of shielding. Scientists run small machines the size of water heaters that zap containers full of seeds, greenhouses that expose young plants and special fields that radiate row upon row of mature plants. In Japan, one circular field is more than 650 feet wide. A shielding dike some 28 feet high rises around its perimeter.

Dr. Lagoda said a rust fungus threatened the Japanese pear, a pear with the crisp texture characteristic of apples. But one irradiated tree had a branch that showed resistance. He said the Japanese cloned it, successfully started a new crop and with the financial rewards “paid for 30 years of research.”

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Pierre Lagoda, the head of plant breeding and genetics at the International Atomic Energy Agency, showing mutated plants at a greenhouse in Austria.Credit
Herwig Prammer for The New York Times

The payoff was even bigger in Europe, where scientists fired gamma rays at barley to produce Golden Promise, a mutant variety with high yields and improved malting. After its debut in 1967, brewers in Ireland and Britain made it into premium beer and whiskey. It still finds wide use.

“The secret,” reads a recent advertisement for a single malt Scotch whiskey costing $49.99 a bottle, is “the continued use of finest Golden Promise barley and the insistence on oak sherry casks from Spain.”

The atomic agency in Vienna has promoted the method since 1964 in outreach programs with the Food and Agriculture Organization of the United Nations, in Rome.

Starting roughly a decade ago, for instance, the atomic agency helped scientists fight a virus that was killing cocoa trees in Ghana, which produces about 15 percent of the world’s chocolate. The virus was killing and crippling millions of trees.

In the city of Accra on the Atlantic coast, at the laboratories of the Ghana Atomic Energy Commission, the scientists exposed cocoa plant buds to gamma rays. The mutants included one that endowed its offspring with better resistance to the killer virus.

The scientists planted the resistant variety on 25 farms across Ghana “with no evidence of a resurgence,” M. R. Appaih, executive director of the Cocoa Research Institute of Ghana, told the agency.

The atomic agency had similar success in the Peruvian Andes, where some three million people live on subsistence farming. The region, nearly two miles high, has extremely harsh weather. But nine new varieties of barley improved harvests to the point that farmers had surplus crops to sell.

In 2006, Prof. Gomes Pando won the Peruvian prize for Good Government Practices for her work on the radiation mutants.

In Vietnam, the agency has worked closely with local scientists to improve production of rice, a crop that accounts for nearly 70 percent of the public’s food energy.

One mutant had yields up to four times higher than its parent and grew well in acidic and saline soils, allowing farmers to use it in coastal regions, including the Mekong Delta.

Last year, a team of 10 Vietnamese scientists wrote in an agency journal, Plant Mutation Reports, that the nation had sown the new varieties across more than one million hectares, or 3,860 square miles. The new varieties, they added, “have already produced remarkable economic and social impacts, contributing to poverty alleviation in some provinces.”

Dr. Lagoda said that radiation breeding, though an old technology, was undergoing rapid growth. New methods that speed up the identification of mutants are making radiation breeding even more popular, he said.

“Now it becomes interesting again,” he said of the method. “It’s not a panacea. It’s not the solution. But it’s a very efficient tool that helps us reduce the breeding time.”

Spreading the secret, Dr. Lagoda added as he played with his tiny dice, “is very gratifying because we really, really help people.”

Correction: September 1, 2007

An article in Science Times on Tuesday about the use of radiation to produce mutations of crops misstated the properties of Japanese pears. Although Japanese pears have the crisp texture characteristic of apples, they are not a cross between apples and pears. They are pears, from the species Pyrus pyrifolia.